1. Field
The present invention relates to a headrest adjustment and lock mechanism and method, and in particular to a headrest lock guide assembly, for removably securing a headrest assembly to a vehicle seat, and the associated method of use.
2. Description of the Related Art
A vehicle seat can have a headrest that can be adjusted in its height relative to the seat back to accommodate occupants of various heights. Typically, these adjustable headrests can be locked into one of a plurality of height positions by a spring biased lock.
One example of a headrest lock structure is described in U.S. Pat. No. 7,121,626 to Akehi et al. (Akehi et al.). Referring to FIG. 1A of Akehi et al., a lock plate or lock member 2 can be fitted into one of three lock slots 4a formed in the headrest pole 1 to allow the height of the headrest to be freely adjusted. As shown in FIGS. 4A and 4B of Akehi et al., the lock plate 2 is fixed to a lock-releasing knob 16 that is biased by a spring 5 such that the lock plate 2 is fitted into one of the lock slots 4a. With reference to FIGS. 1A, 1B, 4B and 5B of Akehi et al., a user may increase the height of the headrest relative to the seat back by applying a force upwardly on the headrest until the lock plate 2 engages the flat upper side surface 42 of one of the lock slots 4. In order to lower the headrest relative to the seat back, a user must push the knob 16 against the biasing force of the coil spring to move the lock plate 2 out of engagement with one of the lock slots 4a. 
Many vehicles have seats that can be folded to provide a flat cargo area in the vehicle cabin. In such vehicles, it may be desirable to remove the headrest from the seat when the seat is in the folded position.
In the headrest lock structure disclosed by Akehi et al., the user must apply a force upwardly on the headrest until the lock plate 2 engages the lowest lock slot 4b. Engagement of the lock plate 2 with the lock slot 4b prevents further upward displacement of the headrest. In order to remove the headrest from the seat back, the use must push on the knob 16 and against the bias of the coil spring 5 to disengage the lock plate 2 from the lock slot 4b. Then, the user can remove the headrest by applying an upward force on the headrest while pushing on the knob 16 until the lock slot 4b moves upwardly beyond the lock plate 2.
In contrast to the headrest lock structure of Akehi et al., U.S. Pat. No. 6,655,742 to Ozaki discloses a locking/unlocking mechanism for a headrest H that employs two separate mechanisms—one for adjusting the height of the headrest H and another one for preventing removal of the headrest H from the seat back. The locking/unlocking mechanism of Ozaki includes a stopper notch 10 on a first headrest stay 1, and plural notches 11 on a second headrest stay 1A. First and second headrest holders 2, 2′ supportively receive the respective first and second stays 1, 1A. The second headrest holder 2 is provided with a known headrest vertical adjustment mechanism, as generally designated by M, in the head 2T′ thereof, which works to lockingly engage a selected one of the plural notches 11, so that the user can adjustably raise and lower the headrest H.
In order to remove the headrest H from the seat back, a user has to draw the headrest H upwardly from the headrest holders 2, 2′ until the stopper notch 10 until the lock member 20 is quickly moved by the biasing force of the springs 25, causing the engagement edge 20C-1 of the lock hole 20C to engage the stopper notch 10. Then, the user should lower the headrest H a slight amount so as to cause disengagement of the stopper notch 10 from the lock hole 20C. Next, an unlocking tool T is inserted into the tool insertion hole 20D to prevent withdrawal of the lock member 20 caused by the biasing force of springs 25 in the unlocking direction. Finally, the user can remove the headrest H from the headrest holders 2, 2′.